I agree. Promoting proper prior planning by the use of concept art would be wise on these forums, or anywhere.
In fact, my animation class was just discussing tonight the importance of drawing out concepts and storyboards before going into any sort of development process.
Sure you could merge this into game design or even 2D art, but I think a whole board dedicated to it would be helpful. Conceptart.org has an entire forum to just that one topic, concept.
For anyone aspiring to go into the industry this would be a practical addition and show that TGC is willing to promote good form in the design/development process.
Maybe to make it broader it could just be the 'concept' board, not specifically concept art. It would be the place where concepts are born and judged to live or die.
"If I have seen a little further it is by standing on the shoulders of Giants" - Isaac Newton
-Computer Animation Major @Baker.edu-